1. Field of Invention
The present invention relates generally to trimmers, and more particularly to a device for trimming a lateral edge of printed products.
2. Description of the Related Art
Following the binding of printed material, such as books, book blocks, brochures, and similar printed products, the unfinished printed material are trimmed to a specified size using a trimming device. Conventional trimming devices are usually positioned at the end of a production line, along which the printed products are sequentially gathered, bound, trimmed and stacked. Such conventional trimmers may also be known as three-knife trimmers. A distinction is often made between trimming methodology by which the trimming devices trim the printed material, i.e., devices operating based on the knife and counter-knife methodology (i.e. the shearing principle), versus those operating with a trimming knife swinging against a softer cutting bar. Regardless of the trimming or cutting methodology, the printed products must first be transported with a conveying system to the trimming position, aligned precisely in this position, and held down securely before the trimming operation can be realized. Once the product has been trimmed, the holding down force is deactivated and the printed product is removed from the trimming region to make way for the next product that arrives. Additional means are required for removing the cuttings generated during the trimming operation. If the cuttings are left in place, for example, they can hinder the alignment of the next printed product to be trimmed, thus resulting in a reduced trimming accuracy or even in unusable printed products. It is also conceivable that the cuttings may be carried along by the printed products and interfere with the ensuing processing operations. The situation is particularly critical when the cuttings are removed from trimming apparatuses where the trimming knives are positioned transverse to the conveying direction for the printed products because the available space must be used for conveying the printed products as well as for removing the cuttings. The requirements to be met for removing the cuttings increase further with higher clocking times and/or shorter cycle times, with increased thickness of the product to be cut, and with wider sections. Present-day trimming apparatuses cannot be operated reliably without auxiliary devices for removing the cuttings.
One widespread conventional solution provides for the use of compressed air nozzles, which are mounted on the movable trimming knife or parts close to the trimming knife and thus follow the movement of the knife. In the process, the compressed air is directed along the back side of the trimming knife and toward the cutting edge of the blade, blowing the cuttings away from the trimming knife. Additional compressed air nozzles, which are also mounted on the trimming knife and are directed toward a collecting cone on a device for suctioning off cuttings, are intended to accelerate the movement of the cuttings for the transport into this cone. This solution, however, has a disadvantage in that the compressed air nozzles directed toward the collecting cone are positioned so far away from the generated cuttings that their effect is inadequate. Further, as a result of air turbulences that form, the removal of cuttings in the direction of the collecting cone is too slow, thus the collisions with the following printed product to be trimmed is often not prevented.
According to a different solution, disclosed in German patent document DE 37 13 897 A1, which is incorporated herein by reference in its entirety, a guiding device with a downward pointing compressed air nozzle for removing the cuttings is mounted on the trimming knife and/or the knife holder itself. Although this solution may be adequate for small sections and long cycle times, as a result of the compressed air that is directed toward the cutting surface of the trimming knife, the cuttings are swirled around in the cutting space that is open toward the bottom and are conveyed away in downward direction with a delayed effect.
The aforementioned devices furthermore have the disadvantage that the elements intended for removing the cuttings, such as compressed air nozzles and guiding devices, are mounted directly on the trimming knife or the knife holder and always occupy the same position relative to the trimming knife. Therefore, these elements move along a curve, analog with the trimming knife, determined by the swing cut of the trimming knife. This limitation strongly curtails the design choices for these elements because of the need to prevent collisions with the devices necessary for conveying the printed products to the trimming table.